Products, such as liquid food, beverages, juices or the like, are often heated and then filled into containers in a warm state for preservation purposes. The filled products in the containers are then cooled down. For this, tunnel recooling apparatuses are often used. Typically, a liquid coolant is used, for example water. The cooled down containers, for example bottles, exiting from the cooling apparatus have a predetermined temperature which is lower than the temperature of the entering containers. After the coolant has entered into contact with the containers in the tunnel cooling apparatus, for example by spraying or irrigating, the coolant is heated due to heat exchange. For heat recovery, a heat exchanger is included in the coolant flow. The coolant is circulated in a circuit for which typically one or several pumps are used. The design of the pump, the apparatuses and temperature are strictly directed by the nominal discharge of the system, i. e. the maximum rating for the system.
In real surroundings of a production plant, the nominal discharge, however, is only reached within restricted periods. For example, the system is operated with different products and different outputs. Moreover, short production gaps and major production interruptions occur. With respect to the bottle outlet temperature of the product downstream of the tunnel recooling apparatus, an adequate cooling result is achieved in real operation. However, thermal yield/heat recovery in the heat exchanger of the coolant flow is often suboptimal.